動詞 assure:

1. make certain of
   同義詞：guarantee, ensure, insure, secure
2. inform positively and with certainty and confidence
   同義詞：tell
3. assure somebody of the truth of something with the intention of giving the listener confidence
4. be careful or certain to do something; make certain of something
   同義詞：see, check, insure, see to it, ensure, control, ascertain
5. cause to feel sure; give reassurance to
   同義詞：reassure
6. make a promise or commitment
   同義詞：promise

1. Her success as an actress was now assured.
   她當演員很成功，已毋庸置疑了。
2. We book early to assure ourselves of seats.
   我們及早訂票以確保有座。
3. I can assure you that your son will be happy here.
   我可以向你保證，你兒子在這里會很快樂的。

as.sure

v.tr.（及物動詞）
as.sured,as.sur.ing,as.sures
To inform positively, as to remove doubt:
向…保證：告知確實如此，以解除懷疑：
例句：
assured us that the train would be on time.
向我們保證火車將會準時到達

To cause to feel sure:
使確信：
例句：
assured her of his devotion.
使她確信他的摯愛

To give confidence to; reassure.
給予信心；使放心
To make certain; ensure:
確實；保證：
例句：
.Nothing in history assures the success of our civilization.(Herbert J. Muller)
.歷史上沒有任何東西保證我們文明的勝利.(赫伯特J.馬勒)

To make safe or secure.
使安全，使穩(wěn)固
Chiefly British To insure, as against loss.
【多用于英國】 給…保險，以防意外

來源：
Middle English assuren
中古英語 assuren
from Old French assurer
源自 古法語 assurer
from Vulgar Latin *assôcôr3re [to make sure]
源自 俗拉丁語 *assôcôr3re [確認]
Latin ad- [ad-]
拉丁語 ad- [前綴，表.朝，向.]
sôcôrus [secure] * see secure
sôcôrus [安全的] *參見 secure

【引伸】
assur.able
adj.（形容詞）
assur.er
n.（名詞）
Assure, ensure, and insure all mean .to make secure or certain.. Onlyassure is used with reference to a person in the sense of .to set the mind at rest.:
Assure,ensure 和 insure 都指.使穩(wěn)固或有把握。. 只是assure 用來指人，有.使某人放心.的意思：
例句：
assured the leader of his loyalty.
使領(lǐng)導(dǎo)確信他的忠誠。

Althoughensure and insure are generally interchangeable, onlyinsure is now widely used in American English in the commercial sense of .to guarantee persons or property against risk..
雖然ensure 和 insure 在一般情況下可以互換， 現(xiàn)在只有insure 廣泛用于美國英語中，商業(yè)中意指.給人或財產(chǎn)保險以防意外。.